A program of second generation prospective studies is proposed to clarify key problems concerning the epidemiology of hypertensive and atherosclerotic diseases, not resolved by the first generation studies. These include the interrelated influences of major risk factors (hypercholesterolemia, hypertension, cigarette smoking) on risk of death from coronary heart disease, cerebrovascular diseases and all causes in population strata other than middle-aged American white males (i.e., young adult and elderly white males, white females, black males and black females in the U.S., as well as white males in Ireland); the role of several other variables as risk factors independent of and additive to the major factors, particularly glycemia, serum uric acid, relative weight, pure systolic hypertension, scores from the Jenkins Activity Survey (Types A & B personality-behavior pattern); resting heart rate, various abnormalities in the resting ECG, nativity, education, marital status; the interrelationships over time among such factors as relative weight, glycemia, uricemia, cholesterolemia, blood pressure (e.g., Is hyperglycemia a risk factor for hypertension in an originally normotensive person?); the predictive power of two or more measurements over years of risk factors, compared to a single measurement; the optimal time intervals for repeat mass public health screening for specific age-sex-race-risk strata of the U.S. population. These questions are to be explored by long-term follow-up to mortality (cause- specific and all causes) of three major population cohorts for whom computerized data files are available: about 40,000 young adult and middle-aged men and women, white and black, screened by the Chicago Heart Association Detection Project in Industry during 1967-72 (over 4,000 screened twice); about 5,000 men followed for years with repeat examinations in the Chicago Peoples Gas Co. and Chicago Western Electric Co. studies; about 20,000 men screened by the Irish Heart Foundation during 1968-72 (re-screening currently in progress). Analytical methods are to be chiefly of the life table type, univariate, multivariate cross-classification, multivariate linear and logistic regression.